ANAHEIM, Calif. — For much of the last decade, the All-Star break was a needed respite from the losing and the frustration of an already lost baseball season for the Mariners.

But this year, it’s different for fans. The break is taking too long. The Mariners can’t get back to playing baseball soon enough. Seattle opens a three-game series with the Angels on Friday night in Anaheim.

Why the impatience?

Well, they are winning. They are relevant. They have legitimate postseason aspirations. That hasn’t been the case for recent teams this late in the season.

Seattle is 51-44. It’s just the fifth time in franchise history that a team has won 50 games or more before the All-Star break. Their .537 winning percentage is the fifth best in the American League. They lead the race for the second American League wild card by 2½ games over the Royals and Blue Jays.

The success wasn’t completely expected. The Mariners figured to be better with the addition of Robinson Cano and the continued development of Kyle Seager and other young players, but this level of winning has exceeded expectations.

The goal of a winning season has been replaced by a berth in the postseason.

“I think this organization has come quite far,” said manager Lloyd McClendon. “I think we’ve accomplished a lot, but in the end we haven’t accomplished anything. But I certainly think we’re headed in the right direction. I think it’s nice for our fans. I certainly think this organization is headed in the right direction.”

McClendon wouldn’t boast that he expected this kind of success. He was still learning about his team when it left spring training on the final day in March.

“I didn’t know what kind of club I had,” he said. “And I didn’t think I would know until we were 50, 60 games into the season, so no, I didn’t think that. I thought our pitching was going to be pretty good. I didn’t know about our offense — I still don’t know about our offense. But I know our pitching’s pretty darn good; our bullpen’s been better than I thought it was going to be. So I like where we are.”

But where are the Mariners?

Yes, they’re winning and they’re in the wild-card hunt now. But can it be sustained? Much has been made of the Mariners’ positive run differential of plus-57. The number is astonishing considering the team is last in the American League in on-base percentage (.300) and on-base plus slugging percentage (.677), second to last in batting average (.245) and fourth to last in runs scored (3.98). How did they do it? Well, for much of the first half, they were hitting close to .290 with runners in scoring position — a pace that cannot be sustained — and the pitching staff has been one of the best in baseball.

The Mariners’ starting rotation ranks second in the AL with a 3.52 earned-run average with Felix Hernandez leading all pitchers with a 2.12 ERA and Hisashi Iwakuma (2.98) and Chris Young (3.15) in the top 25.

The bullpen has been even better. The group, anchored by Fernando Rodney, who leads the American League in saves with 27, has a 2.39 ERA, which is the lowest in the majors. The unit has allowed the fewest number of extra-base hits.

The pitching has been good enough to carry Seattle through its offensive droughts. But can that formula carry the Mariners into the postseason?

“If we continue to pitch the way we’re pitching, and if we stay healthy from an offensive standpoint, we’ve got as good a shot as anybody,” McClendon said. “Do we have challenges? Absolutely we have challenges. We all know that. I know this: When you can shut down other teams, it makes those challenges a little easier to climb. So far our pitching’s been shut-down type of pitching, so we’ll see. We’ll see.”

McClendon is also waiting to see if general manager Jack Zduriencik will give him some help via midseason trades. The Mariners have considered adding Phillies outfielder Marlon Byrd and have also been linked to acquiring Tampa’s Bay ace pitcher David Price and utility player Ben Zobrist.

Zduriencik said he believes there will be a few moves made to capitalize on the surprising start. It would be difficult to maintain this pace without reinforcements.

And if they don’t?

“I really do think we have enough in that locker room to win,” said third baseman Kyle Seager. “We won in the first half. We got enough in there to continue to compete and win.”

The Mariners’ solid series win over Oakland to end the first half of the season was a good example for Seager.

“That’s the best team in baseball and they’ve been the best team in our division the last few years,” he said. “With our pitching, the way we match up with anybody with those arms, we are going to be in every game. It’s up to us to score some runs.”

No matter what happens roster-wise, Seager believes the players can’t let the heightened expectations get to them.

“I think you just keep playing,” he said. “You are going to go on your runs, you stay where you are at, you play the way you play and you’ll have a big run. It’s something where if you press or push, you’ll move backward.”

AL wild-card standings

The top two wild-card teams make the postseason and play each other in a one-game playoff. If the postseason started now, the Angels would host the Mariners. A look at the teams chasing the AL West rivals:

Ryan Divish: 206-464-2373 or rdivish@seattletimes.com; on Twitter: @RyanDivish. Ryan Divish covers the Mariners and offers his perspective all season. He gives his inside look at Major League Baseball and power rankings every Sunday.